Hearing aid detection

ABSTRACT

A hearing aid compatible portable electronic audio device is configured to automatically determine whether or not the device is being used by a hearing impaired user who is wearing a hearing aid, and select a mode of operation based on this determination. The device includes a proximity sensor and a magnetic field sensor. The proximity sensor is used to detect a change in distance of the device to the user&#39;s ear. The magnetic field sensor is used to detect a change in magnetic field caused by the device moving relative to the hearing aid. The device selects between a normal audio mode of operation and a hearing aid compatible mode of operation based on both the change in detected distance and the change in detected magnetic field. Other embodiments are also described and claimed.

This application is a continuation of co-pending U.S. application Ser.No. 13/196,770 filed on Aug. 2, 2011.

An embodiment of the invention relates to a portable audio device thatdetects the presence of a hearing aid and provides an output signalaccording to the presence or absence of the hearing aid. Otherembodiments are also described.

BACKGROUND

Typically, someone who suffers from hearing loss wears a hearingassistive device, such as a hearing aid. Hearing aids are electroacoustical devices worn inside the ear to compensate for a hearingimpairment by amplifying the local sound field. Generally, hearing aidsoperate in either a microphone mode or a telecoil mode. In themicrophone mode, sound waves incident upon a microphone that isintegrated in the hearing aid are converted to an electrical audiosignal. In the telecoil mode, an induction coil (also referred to as atelecoil or T-coil) which may also be inside the hearing aid picks upthe local magnetic field that has been modulated by the receiver(earpiece speaker) of a telephone handset. In either mode, the resultantelectrical audio signal that has been picked up is subsequentlyprocessed, amplified and converted to sound (by a small speaker insidethe hearing aid) that can be heard by the user.

Hearing aids do not always function well with some portable audiodevices, such as mobile phones. One problem experienced when using ahearing aid in conjunction with a mobile phone is that the microphoneinside the hearing aid may pick up unwanted ambient acoustic noise fromthe surrounding background environment, in addition to the desiredspeech coming from the mobile phone earpiece speaker (receiver), whichmakes it difficult for the user to discern the desired speech. However,when a hearing aid is switched to the T-coil mode, the hearing aidmicrophone may be deactivated, and the T-coil inductively couples theoutput audio signal (from a speaker in the mobile phone) to the hearingaid. As such, environmental or background acoustic noise is notamplified by the hearing aid when the T-coil is being used as a pick-up.

Hearing aid compatible (HAC) mobile phones are becoming more commonlyavailable to the public. In addition to the typical acoustic receiver,HAC phones may also include a separate loop of wire (referred to as atelecoil or T-coil) for inductive coupling with the T-coil of a nearbyhearing aid. Such phones are thus compatible with both the microphone ofa hearing aid and its T-coil. These mobile phones traditionally includea selector switch that enables a user to manually select a HAC mode ofoperation. In that mode of operation, the audio processing applied to anaudio signal may be modified to change the phone's audio frequencyresponse so as to better accommodate the microphone of a hearing aid.Another change that may be made when the HAC mode has been selected isto allow the processed audio signal to drive a telecoil inside themobile phone.

However, a user may find having to manually select the mode of operationof the mobile phone inconvenient and time consuming. For example, a userwithout a hearing impairment may wish to hand the mobile phone over to aperson who is wearing a hearing aid, during an on-going call forinstance. In this case, the user would need to manually select the HACmode of operation before handing the phone over to the person wearingthe hearing aid. Accordingly, automatic techniques for detecting thepresence of a nearby hearing aid have been suggested.

SUMMARY

In an embodiment of the invention, a portable audio device is configuredto automatically select between a normal mode of operation and a hearingaid compatible mode of operation, where the latter configures the audiodevice with one or more changes that improve its compatibility with ahearing aid during an audio session (e.g., a phone call). The deviceincludes a proximity sensor having an emitter and a receiver, and amagnetic field sensor. The proximity sensor is used to detect a changein distance of the device to an ear of a user. The magnetic field sensoris used to detect a change in the local magnetic field that has beencaused by the device moving relative to a hearing aid that is worn bythe user. A data processor selects the mode of operation based on thechange in distance detected using the proximity sensor and the change inthe local magnetic field detected using the magnetic field sensor. Forexample, the processor may select the hearing aid compatible mode ofoperation when it detects a decrease in the distance of the device fromthe ear of the user and simultaneously detects an increase in magneticfield caused by the device moving toward the hearing aid. Thissimultaneous decrease in detected distance and increase in detectedmagnetic field indicates that the device is most likely moving towardsan ear of a user who is wearing a hearing aid. On the other hand, theprocessor may select the normal mode of operation when it detects anincrease in the distance of the device from the user's ear or when itdetects a decrease in the magnetic field caused by the device movingaway from the hearing aid. Thus, the device automatically switchesbetween the two modes of operation without requiring the user tomanually select the mode of operation each time the user wants to changebetween a normal mode and hearing aid compatible mode. To improve thecertainty of the mode selection decision, motion data as provided by aposition, orientation or movement sensor in the device can be analyzedto for instance detect a simultaneous change in orientation.

While in the hearing aid compliant (HAC) mode, the spectral contentand/or overall strength (e.g., total power) of an audio content signalthat is transmitted by the device may be adjusted, to better suit pickup by a hearing aid (rather than directly by the users ear.) The audiocontent may be transmitted either acoustically, by driving a speaker, orinductively by driving a telecoil. In one instance, the readings fromthe proximity sensor, magnetic field sensor and the position,orientation or movement sensor may be analyzed, to find that the deviceis moving away from the users ear but is not sufficiently far to bedeemed a release from the HAC mode. In response to such a finding, theprocessor may signal an increase in the overall strength of thetransmitted audio content signal, in order to maintain a desiredinductive coupling with the T-coil of the hearing aid, or a desiredacoustic coupling with the microphone of the hearing aid.

The above summary does not include an exhaustive list of all aspects ofthe present invention. It is contemplated that the invention includesall systems and methods that can be practiced from all suitablecombinations of the various aspects summarized above, as well as thosedisclosed in the Detailed Description below and particularly pointed outin the claims filed with the application. Such combinations haveparticular advantages not specifically recited in the above summary.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described with reference to thedrawings summarized below. The embodiments of the invention areillustrated by way of example and not by way of limitation in thefigures of the accompanying drawings in which like references indicatesimilar elements. It should be noted that references to “an” or “one”embodiment of the invention in this disclosure are not necessarily tothe same embodiment, and they mean at least one.

FIG. 1 illustrates a hearing impaired user holding an example audiodevice in his hand, namely a smart phone.

FIG. 2 illustrates a human user holding an example audio device againsthis ear.

FIG. 3 is a block diagram of some of the relevant constituent componentsof an example audio device.

FIG. 4 shows graphs of detected proximity data and detected magneticfield data versus time, as a hearing impaired user moves an audio devicetowards his ear.

DETAILED DESCRIPTION

Several embodiments of the invention with reference to the appendeddrawings are now explained. While numerous details are set forth, it isunderstood that some embodiments of the invention may be practicedwithout these details. In other instances, well-known circuits,structures, and techniques have not been shown in detail so as not toobscure the understanding of this description.

FIG. 1 shows a portable audio device 1 being held by a user 2 in amanner that causes the device 1 to be in its normal audio mode ofoperation. The user 2 may be wearing a hearing aid 6 in his ear 3. FIG.2 shows the user 2 holding the device 1 against his ear 3 (during acall). When the device 1 is being held in this manner by a user who iswearing a hearing aid, the device 1 automatically switches to a hearingaid compatible mode of operation. The device 1 may be any one of severaldifferent types of small consumer electronic devices that can be easilyheld in the user's hand and placed near the user's ear 3 during normaluse. In particular, the device 1 may be a hearing aid compatible mobiledevice, such as a cellular phone, a smart phone, or a media player.

In the embodiment shown in FIG. 1 and FIG. 2, the device 1 may have anexterior front face in which there is a front-facing proximity sensor 4.The proximity sensor 4 may be placed next to an earpiece speaker orreceiver 5 inside the housing of the device 1 and aimed in the samedirection as the speaker 5. As will be explained below, the proximitysensor 4 may be used to detect a qualitative or quantitative measure ofthe distance of the device 1 from an external object that is interpretedto be the user's ear 3.

FIG. 3 is a block diagram of relevant electronic components in anexample hearing aid compatible portable audio device 1. The device 1 mayinclude a data processor 10 that interacts with communications circuitry11, user interface 12, display 13, storage 14, memory 15, audio codec16, proximity sensor 4, magnetic field sensor 18, and position,orientation or movement (POM) sensor 19. These components may bedigitally interconnected and used or managed by a software stack beingexecuted by the processor 10. Many of the components shown or describedhere may be implemented as one or more dedicated hardware units and/or aprogrammed processor (software being executed by a processor, e.g. theprocessor 10).

The processor 10 controls operation of the device 1 by executing one ormore programs containing instructions for it (software code and data)that may be in the storage 14. The processor 10 may be an applicationsprocessor and may, for example, drive the display 13 and receive manualuser inputs through the user interface 12 (e.g., a physical keypad orkeyboard, or, alternatively, virtual keys that may be integrated withthe display 13 as part of a single, touch sensitive display panel on thefront face of the device 1). The processor 10 may also control theautomatic switching between the normal audio mode of operation and thehearing aid compatible mode of operation.

Storage 14 provides a relatively large amount of “permanent” datastorage, using nonvolatile solid state memory (e.g., flash storage)and/or a kinetic nonvolatile storage device (e.g., rotating magneticdisk drive). Storage 14 may store data and software components thatcontrol and manage, at a higher level, the different functions of themobile device 1. For instance, in addition to an operating system, theremay be a telephony application 23 that configures a built-in touchsensitive display to look like the keypad of a traditional telephonyhandset, and allows the user to enter a telephone number to be called,or select a previously stored number from a telephone address book. Thetelephony application then causes the needed call signaling to occurthrough a wireless or mobile communications network (e.g., a cellularterrestrial radio communications network), and enables a built-inmicrophone 9 and an earpiece speaker 20 (e.g., earpiece speaker 5—seeFIG. 1) to be connected to the uplink and downlink audio signals of thecall, to enable the user to participate in a two-way live or real-timeconversation with a far-end user during the call. The telephonyapplication 23 may also control the routing of the downlink audio signalto drive an integrated telecoil 21. An operation mode selectionapplication or mode switcher 24 automatically switches from a normalaudio mode of operation to a hearing aid compatible mode when it hasinterpreted the signals from the proximity and magnetic sensors to meanthat a hearing impaired user has just placed the device 1 against hisear. The mode switcher 24 may interface with the telephony application23 so that its processing of the sensor signals is triggered when thetelephony application has been launched, brought to foreground frombackground, or when an outgoing call is initiated or an incoming call isanswered. The mode switcher 24 may also interface with a digital mediafile player application 25 that can play back locally stored and/orInternet streaming digital sound files. In that case, the processing ofthe sensor signals may be triggered when the media player application islaunched, brought to foreground from background, or when a sound filestarts to play.

In addition to storage 14, there may be memory 15, also referred to asmain memory or program memory, which provides relatively fast access tostored code and data that is being executed by the processor 10. Memory15 may include solid state random access memory (RAM), e.g. static RAMor dynamic RAM. There may be one or more processors, e.g. the processor10, that run or execute various software programs, modules, or sets ofinstructions (also referred to as software) that, while storedpermanently in the storage 14, have been transferred to the memory 15for execution, to perform the various functions described above. Itshould be noted that these modules or instructions need not beimplemented as separate programs, but rather may be combined orotherwise rearranged in various combinations. In addition, theenablement of certain functions could be distributed amongst two or moremodules, and perhaps in combination with certain hardwired logic.

The device 1 includes communications circuitry 11 which includescomponents that perform wireless communications for two-way real-time orlive speech conversations and general data or file transfers. Forexample, communications circuitry 11 may include RF communicationscircuitry that is coupled to an antenna, so that the user of the device1 can place or receive a call through a nearby wireless communicationsnetwork base station. The RF communications circuitry may include a RFtransceiver and a cellular baseband processor to process the digitaldownlink and uplink audio signals of the call through a cellularnetwork. In another embodiment, communications circuitry 11 may includeWi-Fi communications circuitry so that the user of the device 1 mayplace or initiate a call using a voice over Internet Protocol (VOIP)connection, accessed through a wireless local area network.

As the device 1 moves, such as when it is shaken or tilted by its user,its position, orientation and/or movement (POM) sensor 19 may reportcontinuous motion data, for instance as changes in linear acceleration(using an accelerometer) and/or turn rate (using a gyro.) This raw datamay then be used to detect both the current orientation of the device(relative to the ground) and any instantaneous changes to thatorientation. The operating system may permit an application, such as themode switcher 24, to register so as to periodically receive raw datafrom the POM sensor 19, and/or notifications of predefined motion events(e.g., the start or stop of shaking.) As explained below, the modeswitcher 24 may use this motion data to, for instance, improve thecertainty of its decision that the device 1 is being held against ahearing aid.

The device 1 may include an audio codec 16 that contains audioprocessing circuitry that may perform as an analog/digital interface tothe microphone 9, the speaker 20, and the telecoil 21. It may includeanalog amplifiers, analog signal conditioning circuitry, and analog todigital and digital to analog conversion circuitry that is needed forinterfacing analog transducer signals with digital processing algorithmssuch as those running on the processor 10 that operate on a digitalaudio signal (also referred to here as the audio output signal or theaudio content signal). The audio processing circuitry may also includeprogrammable digital audio filters to perform signal conditioning uponthe digital audio content in signal. The digital audio content in signalmay be a downlink or uplink communications signal for a call, streamingaudio from a remote server over the Internet, or locally stored digitalaudio being played back (e.g., a locally stored music or video file).

The audio codec 16 may include multiple audio signal processing modesincluding a normal use mode and a hearing aid compatibility (HAC) mode.In the normal mode, an audio out channel of the codec 16 that drives thespeaker 20 is configured into a mode of operation in which the digitalaudio content signal is to be acoustically coupled with a human ear,through the speaker 20. In contrast, in the HAC mode, the codec 16 maybe configured to perform a type of signal processing (upon the digitalaudio content signal or its analog form) that is intended to improveacoustic coupling with a microphone of a hearing aid. Selecting the HACmode may also result in the codec 16 being configured to process theaudio content signal so as to improve inductive coupling with a hearingaid T-coil; in that case, the output processed audio signal is providedto drive the telecoil 21—see FIG. 3.

For acoustic coupling in the normal audio mode, the audio codec 16 maybe configured to process the audio content signal using a first set ofequalization parameters which result in a frequency response that issuitable for acoustic coupling to a human ear (by driving the speaker20). A suitable frequency response may have reduced energy in the middlefrequency range and increased energy in the upper and lower frequencyranges, so that the output audio signal has a relatively flat frequencyresponse over the voice band (i.e., over frequencies ranging from about300 Hz to about 3.4 kHz). The desired audio signal conditioning, appliedto the audio content signal, may be achieved using a programmabledigital audio filter. The coefficients for configuring such a filter maybe computed by the processor 10 and then passed to the audio codec 16,or they may have been predetermined and stored in the audio codec 16 asone of several programmable settings. Other ways of achieving thedesired audio signal conditioning are possible, e.g., analog filters,

For inductive coupling (in the HAC mode), the audio codec 16 may beconfigured to process the audio content signal using a second, differentset of equalization parameters which result in a processed signal thatwill drive the telecoil 21. The second set of equalization parametersyield a frequency response that is suitable for inductive coupling to ahearing aid T-coil. A suitable frequency response may be one thatresults in signal energy being centered around the middle frequencyrange (e.g., around 1 kHz), as typically required for optimal couplingto a hearing aid T-coil.

The telecoil 21 of the device 1 produces a magnetic field of sufficientstrength in the direction of the T-coil of the hearing aid 6 that isworn by the user 3. The telecoil 21 converts an electrical signal fromthe audio processor 16 that contains the audio content, into a magneticsignal that is picked up by a T-coil of the hearing aid 6. The telecoil21 may be positioned in a suitable location in the device 1 so that itcomplies with the Hearing Aid Compatibility Act of 1988. For example,the telecoil 21 may be installed near the speaker 20 and in particularthe earpiece speaker 5, to generate the magnetic field towards theuser's hearing aid when the user places the device 1 against his ear.

The device 1 also includes a proximity sensor 17 that is used to detectthe device's proximity to an object, such as a user's ear. The proximitysensor 17 may be positioned near the speaker 20 within the housing ofthe device 1 and aimed in the same direction as the speaker. Theproximity sensor 17 may include a complementary emitter and detectorpair, such as an infrared (IR) or supersonic emitter and detector pair,or other like sensor. In one embodiment, the proximity or distance of anexternal object relative to the device 1 can be represented by thestrength of a coded signal from the emitter that has been reflected orscattered by the object and then picked up by the detector. Theproximity sensor 17 may thus generate location data or movement data orboth, which may be used by the processor 10 (e.g., while executing themode switcher 24—see FIG. 3) to determine a measure or estimate of thedistance of an object from the device 1. The applications processor 10may continuously monitor the proximity of the device 1 to an object andmay also be able to determine the type of object it is detecting. Thelight from the emitter may be emitted in square wave pulses which have aknown frequency or code, thereby allowing the processor 10 todistinguish between ambient infrared light and light from the emitterwhich has been reflected by an object, such as the user's ear. If noobject is present or the object is beyond a certain distance from thedetector, an insufficient or small amount of emitted light is reflectedback towards the detector, and this may be interpreted by theapplications processor 10 to mean that an object is not present or is ata relatively large distance away from the device 1. When the detectordetects an increase in light intensity of the reflected light, this maybe interpreted by the applications processor 10 to mean an object ispresent within a short distance of the detector. In each case, theproximity sensor is being used to measure the intensity of reflectedlight which is related to the distance between the object which reflectsthe light and the detector in the device 1.

The device 1 also includes a magnetic field sensor 18 that measures theexternal magnetic field that is present in the immediate surroundings ofthe device 1. The magnetic field sensor 18 may be positioned near thespeaker 20 within the housing of the device 1. The magnetic field sensor18 should be sensitive enough to detect changes in the local magneticfield that have been caused by a hearing aid that is in close proximityto the device 1. The sensor 18 may include, for example, a Hall Effectsensor. The sensor 18 may also be used by other applications running inthe device 1, such as an electronic digital compass. The magnetic fieldsensor 18 may be used to continuously monitor the magnetic fieldsurrounding the device 1. The monitored magnetic field may includecontributions from one or more magnetic components inside device 1 thatare near the magnetic field sensor 18, such as the magnet of the speaker20. The monitored magnetic field may also have a contribution from oneor more external magnetic objects or field sources, i.e. found in theexternal environment close to the device 1, such as when the user placesthe device 1 near a hearing aid that is inside his ear. Accordingly,some type of hearing aid detection calibration procedure may be neededto remove, from the “raw” magnetic field signal being monitored, theeffects of interference by certain components and nearby field sources,so as to isolate the magnetic field signal that is caused by the hearingaid.

The proximity data from the proximity sensor 17 and the magnetic fielddata from the magnetic field sensor 18 may be used to determine thedevice's location relative to a hearing aid that is inside a user's ear.Changes in the monitored (detected) proximity may be computed, and thencompared with computed changes in the monitored magnetic field, todetermine when the user 2 has placed the device 1 against his ear 3.Based on having detected such changes regarding the device's locationand the magnetic field, the processor 10 may then select an audio modeof operation of the device 1. The audio codec 16 may then adjust thefrequency response of a filter to which an audio content signal isinput, according to the audio mode of operation that is selected by theprocessor 10, and provides adjusted or processed audio content signalsto the speaker 20, the telecoil 21, or both. Alternatively oradditionally, the device 1 may be configured to respond to the selectedmode of operation by adjusting other signals that are output by thedevice 1. For example, the communications circuitry 11 may be configuredto adjust its radio frequency (RF) emissions depending on the selectedaudio mode of operation. In the hearing aid compatible mode, the RFemissions may be lowered so that the hearing aid will be less likely tobe affected by RF interference.

As explained above, while in the hearing aid compliant (HAC) mode, thespectral content and/or overall strength (e.g., total power) of an audiocontent signal that is transmitted by the device may be adjusted, tobetter suit pick up by a hearing aid (rather than by the users nakedear.) The audio content may be transmitted either acoustically bydriving the speaker 20, or inductively by driving the telecoil 21 (seeFIG. 3). In one instance, the readings from the proximity sensor 17,magnetic field sensor 18 and the POM sensor 19 may be analyzed by themode switcher 24, to find that the device 1 is moving away from theusers ear but is not sufficiently far to justify a release from the HACmode. In response to such a finding, the mode switcher 24 may signal anthe audio codec 16 to increase the overall strength of the transmittedaudio content signal, in order to maintain a desired inductive couplingwith the T-coil of the hearing aid, or a desired acoustic coupling withthe microphone of the hearing aid.

Note that the magnetic and proximity sensors may produce analog outputsignals that can vary continuously or substantially continuously, ratherthan being discrete values, which have quantum, discrete jumps from onevalue to the next value. For example, the proximity sensor 17 maydetermine or provide data that represents a distance which can varycontinuously or nearly continuously in an analog fashion. In the case ofsuch a proximity sensor, the distance may correspond to the intensity ofreflected light which originated from the emitter of the proximitysensor. The magnetic field sensor 18 may determine or provide data thatrepresents a measurement of the magnetic field that is present aroundthe device 1, which may be an analog value. Such analog signals may besampled e.g., under control of the processor 10, at a predeterminedfrequency that is sufficiently high in order to determine that the userhas moved the device 1 and placed it against his ear. For example, thechange in distance and the change in magnetic field resulting from theuser's movements may have a frequency content of less than 20 hertz. Theprocessor 10 may thus sample output values from the sensors at afrequency of at least 40 hertz (the Nyquist rate of 20 hertz). Othersample rates are, of course, possible.

FIG. 4 shows example graphs of smoothed (filtered) proximity data andmagnetic field data versus time, which coincide with a hearing impaireduser moving the device to his ear. As shown in FIG. 4, at time zero whenthe user is holding the device away from his ear (e.g., to look at thedisplay), the proximity data indicates that the device 1 is far from anobject, and the magnetic field data indicates that the magnetic fieldsurrounding the device is low. As the user then moves the device 1towards his car, the proximity data indicates that the distance of thedevice 1 from an object is decreasing. Meanwhile, the detected magneticfield data is simultaneously increasing, due to the magnetic fieldsensor sensing that the device is moving closer to a particular type ofexternal field source (i.e., a hearing aid). When the detected distanceis decreasing at a given rate (slope) and the detected magnetic fielddata is simultaneously increasing at a given rate (slope), the device 1may be switched to a hearing aid compatible mode of operation, so thatit can be used more effectively by the hearing impaired user. The periodof time in which the changes to the distance and magnetic field data(e.g., slopes) may be computed are indicted in this case as beingbetween t₁ and t₂.

The following are operations performed by the personal audio device 1 toautomatically select between a normal mode of operation and a hearingaid compatible mode of operation. The proximity sensor 17 is used tomonitor the distance of the device 1 from an object, and the magneticfield sensor 18 is used to simultaneously monitor the magnetic fieldlevel (of an external field source). The proximity sensor 17, themagnetic field sensor 18, and the POM sensor 19 may be continuouslyobtaining measurements while the device is powered on and active (i.e.,not in sleep mode). The mode switcher 24 may be triggered to beginanalyzing sensor data when the telephony application 23, the digitalmedia file player 25, or other audio application is running in thedevice 1 (see FIG. 3). As another alternative, the monitoring ofdistance, magnetic field, and POM data may begin when the operatingsystem determines that the device 1 has started to move or change itsorientation (using, for example, motion data or motion events from thePOM sensor 19 that is integrated in the device 1).

The proximity sensor 17 may transmit a proximity signal that indicatesthe distance of the device 1 from an object, e.g. the user's ear, to theprocessor 10. By monitoring the proximity signal, the processor 10 cancompute a change in the distance of the device 1 from the user's ear.This may be, for example, part of computing a slope m_(d) in FIG. 4. Themagnetic field sensor 18 may transmit a magnetic field signal thatindicates the measured magnetic field to the processor 10. By monitoringthe magnetic field signal, the processor 10 can compute a change in themagnetic field around the device 1, e.g. as part of a slope m_(r) inFIG. 4. When the processor 10 detects a significant change in thedistance and/or a significant change in the magnetic field, namelylarger than predetermined thresholds, the processor 10 selects a mode ofoperation of the device based on the detected change in distance and/orthe detected change in the magnetic field. The certainty of thisdecision, i.e., to select between the different modes of operation, maybe improved by the mode switcher 24 analyzing the raw POM data and/ormotion events that are occurring during the same period of time t₁ tot₂. The processor 10 then transmits an operation mode signal to theaudio codec 16 that indicates the selected mode of operation. The audiocodec 16 then processes the input audio content signal that is to beprovided to the user according to the selected mode of operation. Theaudio codec 16 provides the processed audio signal to speaker 20, thetelecoil 21, or both.

The following is an example illustrating a decision process that theprocessor 10 may utilize to select a mode of operation. The processor 10(while running the mode switcher 24) may monitor the proximity signal tocompute a change in distance of the device 1 from the user's ear over agiven time interval. This may be the slope m_(d) in FIG. 4, computedsomewhere in the period of time between t₁ and t₂. While the processor10 does not detect a significant change in distance, the process ends,the device 1 remains in its current mode of operation. The mode switcher24 may also have been monitoring POM data and/or motion events over thesame time interval, to find that the device 1 has essentially not movedor changed orientation—that finding would add certainty to the decisionto maintain the current mode of operation.

When the processor 10 detects a significant change in the distance ofthe device 1 from the external object, the processor 10 determineswhether the distance has increased or decreased. An increase in thedistance may indicate that the user has moved the device 1 away from hisear. In other words, the user is no longer holding the device 1 againsthis ear, and thus the device 1 may not need to be in a hearing aidcompatible mode of operation. If the processor 10 detects this increasein the distance of the device 1 from the user's ear, the processor 10may select a normal mode of operation. The mode switcher 24 may alsohave been monitoring POM data and/or motion events over the same timeinterval, to find that the device 1 has suddenly changed from asubstantially vertical orientation to a substantially horizontal one.That finding would add certainty to the decision that the device 1 is nolonger being held against the ear, such that a change in the mode ofoperation is warranted.

On the other hand, a decrease in the distance may indicate that the userhas moved the device 1 towards his ear. This is depicted in FIG. 4 wherethe slope m_(d) is negative in value. If the processor 10 detects such adecrease in the distance, the processor 10 may analyze the magneticfield signal (e.g., within the same period of time from t₁ to t₂) todetermine whether the contribution from an external magnetic fieldsource (expected to be outside the device 1) has sufficiently increased,e.g. over the same period of time that the distance has decreased. Thisis depicted in FIG. 4 where the slope m_(r) is positive in value. Anincrease in the magnetic field (or positive slope) that occurssimultaneously with a decrease in the distance (or negative slope, as inFIG. 4) may indicate that a user who is wearing a hearing aid has movedthe device 1 towards his ear. If the processor 10 computes such a resultthen it may select a hearing aid compatible mode of operation.Otherwise, if the processor 10 detects either no change or a decrease inthe contribution from the external magnetic field source, this mayindicate that the user is not wearing a hearing aid or is moving thedevice 1 away from his hearing aid. In this case, the processor 10 mayselect the normal mode of operation. Note that while analyzing themagnetic field signal, the mode switcher 24 may also have beenmonitoring POM data and/or motion events over the same time interval, tofind that the device 1 has suddenly changed to a substantially verticalorientation. Such a finding would add certainty to the decision that thedevice 1 has just been moved to the-at-the-ear position, such that achange to the HAC mode of operation is warranted.

Note that the above decision process may be triggered by the processor10 detecting an initial change in the proximity or distance of thedevice 1 from an object. Alternatively, or in addition, the decisionprocess may be triggered when the processor 10 detects an initial changein an external magnetic field contribution, or an initial significantand sudden change in orientation (as found through analysis of POM dataand/or motion events.) In such cases, the decision process may thencontinue with the processor 10 detecting that the distance is decreasingwhile the magnetic field is increasing, in which case it may then selecta hearing aid compatible mode of operation. Otherwise, the processor 10may select a normal mode of operation. Once again, the certainty of thedecision process here may be improved based on analysis of POM dataand/or motions events that are occurring in the same time interval asthe changes in proximity and magnetic field data.

While monitoring the proximity signal and the magnetic field signal, theprocessor 10 (while executing the mode switcher 24—see FIG. 3) mayperform some signal conditioning on the proximity signal, the magneticfield signal, or both, prior to computing the changes in distance ormagnetic field (or their respective slopes). The processor 10 may filterthe raw signals from these sensors to, for instance, remove noise. Forexample, the processor 10 may filter the magnetic field signal inaccordance with the audio content signal that is driving the speaker, inorder to remove changes in the signal that are due to interference fromthe speaker 20. Also, the processor 10 may be configured to respond tocertain patterns of changes and/or certain spectral content, in thedistance and the magnetic field signals, in order to isolate orinterpret the relevant data. For example, the expected change indistance and change in magnetic field resulting from the user'smovements may have a frequency or bandwidth of less than 20 hertz. Theprocessor 10 may thus be configured to respond to changes in thedistance and the magnetic field that occur at frequencies of 20 hertz orless, and ignore changes in the distance and the magnetic field thatoccur at frequencies greater than 20 hertz. This may be achieved bypassing the raw sensor signals through a digital low pass filter havinga 20 hertz cutoff frequency.

Embodiments of the invention may include various operations as set forthabove or fewer operations or more operations or operations in an orderthat is different from the order described. The operations may berepresented in machine-executable instructions that cause ageneral-purpose or special-purpose processor to perform theseoperations. That is, the techniques may be carried out in a computersystem or other data processing system in response to its processor,such as a microprocessor, executing sequences of instructions. Such acomputer program may be stored or transmitted in a machine-readablemedium. A machine-readable medium includes any mechanism that provides(i.e., stores and/or transmits) information in a form accessible by amachine (e.g., a computer, network device, personal digital assistant,manufacturing tool, any device with a set of one or more processors,etc.). For example, a machine readable medium includesrecordable/non-recordable media such as, but not limited to, amachine-readable storage medium (e.g., CD-ROMs, magnetic-optical disks,random access memories (RAMs), flash memory, or any type of mediasuitable for storing electronic instructions), or a machine-readabletransmission medium such as, but not limited to, any type of electrical,optical, acoustical or other form of propagated signals (e.g., carrierwaves, infrared signals, digital signals, etc.).

Alternatively, the operations may be performed by specific hardwarecomponents that contain hardwired logic for performing the operations,or by any combination of programmed computer components and customhardware components. Thus, the techniques are not limited to anyspecific combination of hardware circuitry and software or to anyparticular source for the instructions executed by the data processingsystem. In addition, throughout this description, various functions andoperations are described as being performed by or caused by softwarecode to simplify description. However, those skilled in the art willrecognize that what is meant by such expressions is that the functionsresult from execution of code by a processor, such as a microprocessor.

For purposes of explanation, specific embodiments were described toprovide a thorough understanding of the present invention. These shouldnot be construed as limiting the scope of the invention but merely asillustrating different examples and aspects of the invention. It shouldbe appreciated that the scope of the invention includes otherembodiments not discussed in detail above. Various other modifications,changes, and variations which will be apparent to those skilled in theart may be made in the arrangement, operation, and details of theapparatus and methods of the present invention disclosed herein withoutdeparting from the spirit and scope of the invention as defined in theappended claims. For instance, the hearing aid compatible device isdepicted in FIG. 1 and FIG. 2 as a mobile device; however, it mayalternatively be a hearing aid compatible headset, which may be on thatis wirelessly connected to the mobile device or on that is plugged invia cable to an earphone jack of the mobile device. Therefore, the scopeof the invention should be determined by the claims and their legalequivalents. Such equivalents include both currently known equivalentsas well as equivalents developed in the future, i.e. any elementsdeveloped that perform the same function, regardless of structure.

What is claimed is:
 1. A portable audio device suitable for use with ahearing aid, comprising: a proximity sensor to detect a measure ofdistance of the device to an external object; a magnetic field sensor todetect a measure of external magnetic field; data processing circuitrycoupled to the proximity sensor and the magnetic field sensor to computea change in the distance to the external object and a change in theexternal magnetic field, over a same time interval, and then selectbetween a normal audio mode of operation and a hearing aid compatiblemode of operation, based on the computed changes in distance andmagnetic field occurring over the same time interval; audio processingcircuitry having storage in which an audio application program isstored, and a processor to execute the audio application program so asto generate an audio output signal being one of a downlinkcommunications signal for a call, a streaming audio signal from a remoteserver, or locally stored digital audio being played back, wherein theaudio processing circuitry is to process the audio output signalaccording to the selected mode of operation; and a speaker coupled toreceive the processed audio output signal.
 2. The portable audio deviceof claim 1, further comprising: a telecoil coupled to receive theprocessed audio output signal.
 3. The portable audio device of claim 1,wherein in the normal audio mode different audio equalization parametersare applied to process the audio output signal by the audio processingcircuitry than in the hearing aid compatible mode.
 4. The portable audiodevice of claim 1, wherein the data processing circuitry is to detect adecrease in distance of the device to the external object, and anincrease in the external magnetic field, over the same time interval,and the data processing circuitry is to select the hearing aidcompatible mode in response to the detected decrease in distance and thedetected increase in magnetic field occurring over the same timeinterval.
 5. The portable audio device of claim 4, further comprising aposition orientation or movement (POM) sensor, wherein the dataprocessing circuitry is to monitor data from the POM sensor, over thesame time interval in which the increase in magnetic field and decreasein distance are detected, to detect that the device has changedorientation, and to select the hearing aid compatible mode in responseto the detected orientation change.
 6. The portable audio device ofclaim 1, wherein when the data processing circuitry detects a decreasein magnetic field simultaneous with a detected increase in distance, thedata processing circuitry is to select the normal audio mode in responseto both the detected decrease in magnetic field and the detectedincrease in distance.
 7. The portable audio device of claim 6, furthercomprising a position orientation or movement (POM) sensor, wherein thedata processing circuitry is to monitor data from the POM sensor, overthe same time interval in which the decrease in magnetic field andincrease in distance are detected, to detect that the device has changedorientation, and to select the normal audio mode in response to thedetected orientation change.
 8. The portable audio device of claim 1,wherein the speaker is a receiver integrated in a mobile phone handsethousing and wherein the proximity sensor is positioned next to thespeaker and aimed in the same direction as the speaker.
 9. The portableaudio device of claim 1, wherein the data processing circuitry is todetect an increase in distance of the device to an external object, thedata processing circuitry to select the normal audio mode in response tothe detected increase in distance.
 10. A method performed in a portableaudio device, comprising: generating an audio output signal being one ofa downlink communications signal for a call, a streaming audio signalfrom a remote server, or locally stored digital audio being played back,by a processor in the device executing an audio application program thatis stored in the device; detecting a change in distance of the device toan external object, by processing a proximity sensor signal over aperiod of time; detecting a change in an external magnetic field, byprocessing a magnetic field sensor signal over the period of time; andselecting between a normal audio mode of operation and a hearing aidcompatible mode of operation based on the detected change in distanceand the detected change in magnetic field over the period of time,wherein the audio output signal is generated differently according tothe selected mode of operation.
 11. The method of claim 10, wherein theaudio output signal is an audio signal that drives a speaker, the methodfurther comprising: filtering a magnetic field sensor signal inaccordance with the audio signal to remove interference from thespeaker.
 12. The method of claim 10, wherein selecting the mode ofoperation comprises: selecting the hearing aid compatible mode inresponse to simultaneously detecting an increase in magnetic field and adecrease in distance over the period of time.
 13. The method of claim12, wherein the audio output signal is generated for driving a speakerfor acoustic coupling to a microphone of a hearing aid.
 14. The methodof claim 12, wherein the audio output signal is generated for driving atelecoil for inductive coupling to a telecoil of a hearing aid.
 15. Themethod of claim 12 further comprising detecting a change in orientationof the device, and wherein selecting the mode of operation comprisesselecting the hearing aid compatible mode in response to detecting thechange in orientation in the period of time.
 16. The method of claim 10,wherein selecting the mode of operation comprises: selecting the normalaudio mode in response to simultaneously detecting a decrease inmagnetic field and an increase in distance to the external object,wherein the detected decrease and the detected increase have a bandwidthless than twenty (20) hertz.
 17. The method of claim 16, wherein theaudio output signal is for driving a speaker for acoustic coupling to ahuman ear.
 18. The method of claim 16 further comprising detecting achange in orientation of the device in the period of time, and whereinselecting the mode of operation comprises selecting the hearing thenormal audio mode in response to simultaneously detecting that thedevice has change orientation.
 19. An article of manufacture,comprising: a non-transitory machine-readable storage medium havingstored therein instructions that program a processor, the processorbeing a component of a portable audio device, to a) receive magneticfield data from a magnetic field sensor and proximity data from aproximity sensor, b) compute a distance change from the proximity dataand a magnetic field change from the magnetic field data over a sametime interval, and c) select between a normal audio mode of operationand a hearing aid compatible (HAC) mode of operation based on thecomputed changes occurring over the same time interval, and wherein thestorage medium has further stored therein an audio application programthat programs the processor to generate an audio output signal being oneof a downlink communications signal for a call, a streaming audio signalfrom a remote server, or locally stored digital audio being played back,wherein the audio output signal is generated according to the selectednormal audio or hearing aid compatible mode of operation.
 20. Thearticle of manufacture of claim 19, wherein the processor is to selectthe HAC mode of operation in response to determining that the device hasbeen placed against an ear of a user with a hearing aid therein, basedon having computed a simultaneous increase in magnetic field anddecrease in distance, and wherein in the HAC mode the audio outputsignal is adapted for one of acoustic coupling to a microphone of ahearing aid or inductive coupling to a T-coil of a hearing aid.
 21. Thearticle of manufacture of claim 20, wherein the storage medium hasstored therein further instructions that program the processor toreceive motion data from a position, orientation or movement sensor, andanalyze the received proximity, magnetic field and motion data to findthat the device is moving away from the user's ear but is notsufficiently far to signal a release from the HAC mode, and in responsesignal an increase in strength of the audio output signal.
 22. Thearticle of manufacture of claim 21, wherein the processor is to selectthe normal audio mode of operation in response to determining that thedevice has been moved away from the ear of the user with the hearing aidtherein based on having computed a simultaneous decrease in magneticfield and an increase in distance and wherein the in the normal audiomode the audio output signal is adapted for acoustic coupling to a humanear.
 23. The article of manufacture of claim 20, wherein the processoris to select the normal audio mode of operation in response todetermining that the device has been moved away from the ear of the userwith the hearing aid therein based on having computed a simultaneousdecrease in magnetic field and an increase in distance and wherein inthe normal audio mode the audio output signal is adapted for acousticcoupling to a human ear.